Apparatus for simulating a flame



March 10, 1970 M. T. FORD 3,500,126

APPARATUS FOR SIMULATING A FLAME Filed Nov. 19, 1968 INVENTOR. MIC/M51. 7'. F020 United States Patent 3,500,126 APPARATUS FOR SIMULATING A FLAME Michael T. Ford, Box 1266, South Lake Tahoe, Calif. 95705 Filed Nov. 19, 1968, Ser. No, 776,978 Int. Cl. Hb 37/02, 39/04, 41/02 US. Cl. 315-209 Claims ABSTRACT OF THE DISCLOSURE Apparatus according to the present disclosure comprises input attachment means adapted to be connected to a supply of alternating current and output attachment means adapted to support and connect to an incandescent lamp. Converter means is connected to the input means to convert alternating current to direct current, and oscillator means is connected to the converter means to supply an alternating signal having a frequency which is different from the frequency of the alternating current and any harmonic thereof. Switch means, such as an SCR, is connected between the input and the output means and has its control electrode connected to the oscillator means. An incandescent lamp connected to the output means will fluctuate between 3 and 30 c.p.s. to simulate the flicker of a flame.

This invention relates to a device for fluctuating the frequency of AC current connected to incandescent lamps to simulate flame flicker frequency.

In restaurants, homes, and other similar places it is considered esthetically pleasing to provide candle-light. One reason that candles are esthetically pleasing is the flicker elfect produced by the candle flame. However, due

to stringent fire regulations, it is not always possible to provide flaming candles for decorative purposes. Accordingly, lamps have been used in place of candles, the lamp bases being shaped like candles and the lamp bulbs being shaped like the candle flame. Together, such lamp bases and bulbs have provided a pleasing effect, but not completely like that of a burning candle.

One reason for the failure of such lamps to provide the true effect of a candle is that the lamp bulbs are ordinarily illuminated by a constant 60 c.p.s. power source, while a candle flame tends to flicker at a frequency which randomly varies between 3 and 30 cycles per second.

It is an object of the present invention to provide apparatus for fluctuating AC power so that incandescent lamps connected to such power will flicker at a rate so as to simulate a flame.

Another object of the present invention is to provide a lamp base with a device for fluctuating AC power to a bulb supported by the base so that the lamp base and bulb will simulate a candle.

Another object of the present invention is to provide a device for inserting into a receptacle of a lamp structure which device varies the power to the lamp bulb in such a manner as to cause the bulb to simulate a flame.

According to the present invention, a circuit is provided having an input adapted to be connected to a source of ordinary house current and having an output adapted to be connected to an incandescent bulb. A DC power converter is connected to the input and one or more oscillator stages are connected to the DC converter. Preferably, the frequency of oscillation of each oscillator is close to, but not ekactly '60 cycles per second. Switch means is connected to the output and to the oscillator in such a manner that the power delivered to the output fluctuates so that a lamp connected to the output will flicker to simulate a candle.

According to one optional and desirable feature of the present invention, the entire circuit is housed in a housing adapted to be received into a lamp receptacle. The housing also includes a receptacle to which an incandescent lamp may be assembled.

Another optional and desirable feature of the present invention is to provide means for selectively altering the frequency of oscillation as well as the average power delivered to the output.

The above and other features of this invention will be fully understood from the following detailed description and the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a circuit in accordance with the presently preferred embodiment of the present invention;

FIG. 2 is a graphic representation of wave forms at various points in the circuit illustrated in FIG. 1;

FIG. 3 is a schematic diagram of a modification of the circuit illustrated in FIG. 1;

FIG. 4 is a side view elevation partly in cutaway crosssection of a housing containing a circuit according to the present invention, which housing is capable of being assembled to a receptacle of a lamp base and is capable of receiving a socket portion of a lamp bulb; and

FIG. 5 is a side view elevation, partly in cutaway crosssection of a lamp base having a lamb bulb assembled thereto and having a circuit in accordance with the present invention mounted therein.

Referring to the drawings and particularly to FIG. 1, there is illustrated a circuit 10 having an input attachment means 12 and an output attachment means 14. Input attachment means 12 is adapted to be connected to a source of house current, for example 60 cycle, volt alternating current. As will be more fully understood hereinafter, input attachment means 12 may be a plug adapted to be received by an ordinary wall receptacle of an alternating current power system or may be a socket adapted to be assembled to a receptacle of a lamp. Input attachment means 12 includes a pair of contacts, one of which is connected to ground 16 and the other of which is connected via conductor 18 to one contact of output attachment means 14. As will be more fully understood hereinafter, attachment means 14 is preferably -a receptacle adapted to receive the base or socket of a lamp bulb 84.

DC power converter 20 is connected to conductor 18 and comprises diode 22 connected to conductor 18, resistor 24 connected to diode 22, and capacitor 26 connected between resistor 24 and ground 16. The output of DC converter 20 is connected via conductor 28 to oscillators 30 and 30. As will be more fully understood hereinafter, the number of oscillators 30 may vary but for most purposes only one or two oscillators need be used. The type of oscillator may vary in accordance with part cular design requirements, but it has been found that relaxation and phase-shift oscillators are most desirable. Each oscillator 30 and 30' is identical, so that only oscillator 30 will be described in detail, the corresponding parts of oscillator 30' being referenced on the drawings by the prime of the reference numeral of the corresponding part in oscillator 30.

Oscillator 30 is shown as a relaxation oscillator which comprises a resistor 32 connected to conductor 28. Transistor 34 has its collector connected to resistor 32 and its emitter connected to ground 16. The base of resistor 32 is connected via resistor 36 to the collector of transistor 34, and to ground through capacitor 38 and resistor 40. The collector of transistor 34 is also connected to ground through capacitor 42 and resistor 44. Capacitor 46 is connected between the junction of capacitor 3 8 and resistor 40 and the junction of capacitor 42 and resistor 44. Resistors 40 and 44 may be variable resistors having their variable contacts ganged together. Alternatively, resistors 40 and 44 may be fixed resistors.

The output of oscillators 30, 30 is connected through capacitor 48 to conductor 50 which in turn forms the input to switching circuit 52.

Switching circuit 52 comprises a thyristor 54, such as a triode AC semiconductor switch (TRIAC) or silicon controlled rectifier (SCR), having its cathode connected to ground 16 and its anode connected via conductor 56 to the second contact of output attachment means 14. Capacitor 58 is connected between the gate electrode of SCR 54 and ground 16, and resistor 60 is connected between the gate and anode electrodes of SCR 54.

Referring to FIGS. 1 and 2, the operation of the circuit illustrated in FIG. 1 may be readily explained. In FIG. 2 there is illustrated waveforms a, b and c which correspond to the waveform of the signal at points a, b and c, respectively, in the circuit illustrated in FIG. 1. In operation, a source of power of alternating current, for example 60 cycle, 110 volt alternating current is connected to the circuit via input attachment means 12. An incandescent lamp 84 is connected to output attachment means 14. By way of example, the lamp may be threaded into a threaded receptacle 142 as illustrated in FIGS. 4 and 5. Other means of attachment may be used, such as by the well-known bayonet-type plug and socket. The alternating current appearing on conductor 18 is illustrated as signal (a) in FIG. 2. This signal is a sinusoidal, continuously varying alternating current. Signal (a) is applied across SCR 54 in switching circuit 52 through the lamp connected to attachment means 14. At the same time, the alternating current (a) is applied to DC converter 20 which rectifies the signal and converts it to direct current which in turn is applied to one or more oscillators 30.

Assuming that the circuit includes only one oscillator 30, the rectified current appearing on conductor 28 is applied to the oscillator circuit 30 which is tuned to some frequency other than 60 c.p.s. or a harmonic thereof. The frequency of oscillation of oscillator 30 may be close to but not equal to 60 cycles per second and may not be a harmonic of 60 cycles per second. By way of example, a frequency range between 1 and 40 cycles per second has been found to be suitable for relaxation oscillators, although other frequencies may be available from other oscillators. Ordinarily, however, the frequency of oscillator 30 will not exceed 500 c.p.s. The frequency of oscillation of oscillator 30 may be readily adjusted by means of adjustable resistors 40 and 44 or may be selectively fixed by selecting proper values for resistors 40 and 44. In addition, and as will be more readily understood hereinafter, resistor 40 is preferably a heat sensitive resistor whose value varies in accordance with heat from the lamp attached to attachment 14 so that the rate of oscillation of oscillator 40 likewise varies.

The signal output from oscillator 30 is depicted at (b) in FIG. 2 and is applied to the input or gate electrode of SCR 54.

To operate SCR 54, the signal appearing at both the anode and the gate electrodes must be positive for the SCR to conduct, and the SCR will cease conducting when the signal at the anode is negative.

The conduction of SCR 54 is controlled by oscillators 30 and resistor 60. Waveform (c) in FIG. 2 illustrates the signal impressed on the control electrode of SCR 54. Waveform (c) is at exactly the same frequency as waveform (a), but is phase-shifted from signal (a) by some amount dependent upon the time constant determined by the R-C combination of resistor 60 and capacitor 58. Waveforms (b) and derived by oscillators 30 and R-C network 58, 60, respectively, are added together to form waveform (d) which in turn is impressed on the control electrode of SCR 54.

The phase relationship of waveform (c) to waveform (a) is dependent upon the value of resistor 60. If resistor 60 is small, for example, Zero, there is, essentially a short-circuit across resistor 60, and waveform (c) follows exactly waveform (a), and SCR 54 conducts during the entire positive ha1f-cycle of signal -(a). Hence, under these conditions half power is passed on to lamp 84. If the value of resistor 60 is different from zero, the R-C time constant of resistor 60 and capacitor 30 cause signal (0) to be phase-shifted from signal (a) and, when signals (b) and (c) are added together the complex waveform of signal (d) is derived.

Resistor 60 is connected into switch 52 in such a manner that the resistor operates as a lamp dimming circuit. It can be shown that the average power delivered to the lamp over an extended period of time is determined by the phase relationship between signals (a) and (0). Hence, controller of resistor 60 may be utilized as a variable dimmer control for the lamp control circuit.

Signal (d) is impressed on the control electrode of SGR 54, which will begin to conduct when both signals (a) and (d) are positive and will cease to conduct when signal (a) swings negative.

The signal (e) is the waveform of the current passed by SCR 54 and varies in duration of each half cycle as well as peak amplitude. By adjusting resistors 40 and 44, the frequency of oscillators 30 may be adjusted, and by adjusting resistor 60 the average power may be adjusted. Thus, the power passed by each half-cycle may be fluctuated so that the lamp connected to attachment means 14 will flicker to simulate the flicker of a flame.

Although the lamp bulb is, to the casual observer, randomly flickering, it can be shown that for fixed values of the electrical components, the flicker rate will be repetitive. For example, the flicker rate might repeat frequency patterns on a two or three minute cycle. To make the frequency pattern more complex, two or three oscillators of similar or different types may be connected in parallel to switching circuit 52 and each tuned to a slightly different frequency to drive the switching circuit. Also, by utilizing a heat sensitive resistor for resistor 44, in the oscillator, the frequency of oscillation can be made dependent upon the heat generated by the lamp attached to attachment means 14 and thereby to the average power passed by circuit 10. Thus, resistor 44 is preferably in close proximity to the lamp.

The lamp and resistor 44 can be adjusted to work against each other so that when circuit 10 is passing a relatively high average power the heat dissipated by the lamp operates on resistor 44 to reduce the average power being passed by the circuit, and conversely when the circuit passes a relatively low average power, the lamp dissipates a lower amount of heat thereby permitting resistor 44 to cool to increase the power passed by the circuit. In this manner the frequency pattern appears completely random to the casual observer.

FIG. 3 illustrates a circuit diagram of a modification of the circuit illustrated in FIG. 1. As in the case of FIG. 1, the input attachment means 12 and output attachment means 14 shown in FIG. 3 may be any suitable input and output attachment means. Furthermore, DC converter 20 and switching circuit 52 are identical to that illustrated in FIG. 1 and need no further description. As in the case of FIG. 1, one contact of input attachment means 12 is connected via conductor 18 to a contact of output attachment means 14, and the other contact of input attachment means 12 is grounded at 16. The other contact of output attachment means 14 is connected via conductor 56 to the output of switching circuit 52. DC converter 20 is connected to conductor 18 and its output is connected via conductor 28 to the inputs of oscillators 30a and 30a. The outputs of Oscillators 30a and 30a are connected to conductor 50 which provides the input to switching circuit 52. The only significant difference between the circuit illustrated in FIG. 1 and that illustrated in FIG. 3 resides in the specific circuitry of the oscillator. Since the oscillators 30a and 30a are identical, only oscillator 30a will be described in detail.

Oscillator 30a comprises a unijunction transistor 70 having one electrode connected to conductor 28 and the other electrode connected via resistor 72 to ground 16. The control or emitter electrode of unijunction transistor 70 is connected via capacitor 74 to conductor 50. Resistor 76 is connected between the control electrode of the unijunction transistor 70 and conductor 28 and capacitor 78 is connected between the control electrode and ground.

As illustrated in FIG. 3, resistor 76 may be an adjustable resistor which is adjusted so that oscillator 30a oscillates at a frequency other than 60 c.p.s. or one of its harmonics as hereinbefore described in connection with FIG. 1. Preferably, resistor 76 is a heat sensitive resistor capable of having its resistance value altered by heat from the lamp connected to output attachment means 14 as hereinbefore described in connection with resistor 44 in FIG. 1.

In FIG. 4 there is illustrated a device adapted to be threaded into the existing receptacle or socket of a lamp and adapted to receive the receptacle portion of a light bulb. In particular, the device includes a receptacle housing 80 containing circuit 1011, which may be one of the circuits illustrated in FIGS. 1 and 3. The circuit is connected to input attachment means 12a which comprises a threaded socket adapted to be received by the receptacle (not shown) of an existing lamp structure. The output attachment means comprises a threaded receptacle 14a adapted to receive the base or socket portion of an incandescent lamp or light bulb (not shown). Due to the fact that the circuit is constructed of solid state elements, the entire circuit may be encapsulated into a volume as small as one cubic inch, and could be made even smaller by well-known thin-film or other techniques.

In the use of the device illustrated in FIG. 4, threaded portion 12a is threaded into the existing receptacle of an existing lamp base (not shown) and a light bulb (not shown) is threaded into receptacle 14a. When the lamp is switched on by means of a switch (not shown), power delivered through input attachment means 12a to the circuit causes the circuit a to pass power to output receptacle 14a and to the lamp assembled thereto, to cause the lamp to flicker at a frequency which varies between about 3 and 30 c.p.s. and causing the power to fluctuate in magnitude so as to simulate the flicker frequency of a candle. Since the circuit is in close proximity to the lamp, heat from the lamp causes the heat sensitive resistors therein to vary the frequency of oscillation of the circuit. Thus, fluctuating power is delivered to the lamp which flickers at a rate which appears random to the casual observer.

In FIG. 5 there is illustrated a lamp structure 82 containing circuit 10 which may be similar to that illustrated in FIGS. 1 or 3. Circuit 10 is connected by means of suitable line cord to an input attachment means 12b such as a plug for inserting into a wall receptacle. Circuit 10 is also connected via suitable wires to receptacle 14 into which lamp 84 is threaded.

In the case of FIG. 5, controller knob 90 is mounted in such a position as to be accessible, so that the average power to the lamp may be selectively adjusted as hereinbefore described. The number of lamps connected to circuit 10 in FIG. 5 may vary in accordance with taste, but it is to be understood that all lamps so connected will flicker at identical rates and in unison. For this reason, where a plurality of lamps is employed, it is most desirable to use a like plurality of circuits 10 to fluctuate the power to each lamp independently of the others.

The present invention thus provides a device for fluctuating the frequency of illumination of a lamp so as to cause the lamp to flicker to simulate the flicker of the flame of a candle. Thus, with the present invention, lamps may be utilized in place of candles to achieve the same esthetic qualities as candles. The circuit according to the present invention is easily manufactured and is simple and effective in operation.

This invention is not to be limited by the embodiment shown in the drawings and described in the description, which is given by way of example and not of limitation, but only in accordance with the scope of the appended claims.

What is claimed:

1. A device for providing fluctuating power to an incandescent lamp so as to energize said lamp in such a manner that the lamp provides a luminous output similar to that of a flame, said device comprising: input attachment means adapted to be connected to a source of alternating current; converter means connected to said input means for converting alternating current to direct current; oscillator means connected to said converter means for converting said direct current to an alternating signal having a frequency'different from the frequency of said alternating current or a harmonic thereof; output means including a lamp receptacle for supporting and providing connection to an incandescent lamp; and switch means having a first primary electrode connected to said input means, a second primary electrode connected to said output means, and a control electrode connected to said oscillator means, said switching means initiating conduction of said alternating current between said input and output means when said alternating current is of one polarity and said alternating signal exceeds a design level and said switching means ceases conduction when said alternating current is of a polarity opposite said one polarity, whereby the power of said alternating current is fluctuated at a rate which varies between 3 and 30 cycles per second.

2. Apparatus according to claim 1 wherein said oscillator means includes heat sensitive means responsive to heat generated by said lamp for changing the frequency of oscillation of said alternating signal.

3. Apparatus according to claim 1 further including phase-shift means connected to said control electrode and one of said primary electrodes of said switch means, said phase-shift means being operable to impress .a second signal on said alternating signal to determine said design level, said second signal being of the same frequency as said alternating current, said phase-shift means including means for shifting the phase of said second signal relative to said alternating current.

4. Apparatus according to claim 3 wherein said phaseshift means comprises a resistor and a capacitor connected in series between said first and second primary electrodes and said control electrode is connected to the junction of said resistor and capacitor.

5. Apparatus according to claim 1 wherein said switching means includes a semi-conductor switch having a gate electrode connected to said oscillator means and having anode and cathode electrodes connected between said input and output means.

6. Apparatus according to claim 1 wherein said oscillator means comprises a plurality of oscillators, each of said oscillators being connected in parallel to said converter means and to said switching means, said oscillators providing separate alternating signals each having respective different frequencies and each being different from the frequency of said alternating current or a harmonic thereof.

7. Apparatus according to claim 1 wherein said input attachment means comprises a socket adapted to be assembled to a lamp receptacle of an existing lamp structure, said socket being of the same type as the lamp receptacle for supporting said incandescent lamp, and a housing supporting said input and output attachment means and enclosing said converter means, oscillator means, and switching means.

8. Apparatus according to claim 7 further including phase-shift means connected to said control electrode and one of said primary electrodes of said switch means, said phase-shift means being operable to impress a second signal on said alternating signal to determine said design level, said second signal being of the same frequency as said alternating current, said phase-shift means including means for shifting the phase of said second signal relative to said alternating current.

9. Apparatus according to claim 8 wherein said oscillator means includes heat sensitive means responsive to heat generated by said lamp for changing the frequency of oscillation of said alternating signal.

10. Apparatus according to claim 9 wherein said oscillator means comprises a plurality of oscillators, each of said oscillators being connected in parallel to said converter means and to said switching means, said oscillators providing separate alternating signals each having respective different frequencies and each being different from the frequency of said alternating current or a ham monic thereof.

11. Apparatus according to claim 1 wherein said input attachment means comprises a plug adapted to be assembled to a wall receptacle connected to a household supply of alternating current, and a lamp structure supporting said lamp receptacle and enclosing said converter means, oscillator means and switching means.

12. Apparatus according to claim 11 further including phase-shift means connected to said control electrode and one of said primary electrodes of said switch means, said phase-shift means being operable to impress a second signal on said alternating signal to determine said design level, said second signal being of the same frequency as said alternating current, said phase-shift means including means for shifting the phase of said second signal relative to said alternating current.

13. Apparatus according to claim 12 wherein said oscillator means includes heat sensitive means responsive to heat generated by said lamp for changing the frequency of oscillation of said alternating signal.

14. Apparatus according to claim 13 wherein said oscillator means comprises a plurality of oscillators, each of said oscillators being connected in parallel to said converter means and to said switching means, said oscillators providing separate alternating signals each having respective different frequencies and each being different from the frequency of said alternating current or a harmonic thereof.

15. In combination: an incandescent lamp adapted to be energized by fluctuating power to provide a luminous output similar to that of a flame; and a device connected to and supporting said lamp for providing said fluctuating signal, said device comprising: input attachment means adapted to be connected to a source of alternating current, converter means connected to said input means for converting alternating current to direct current, oscillator means connected to said converter means for converting said direct current to an alternating signal having a frequency different from the frequency of said alternating current or a harmonic thereof, output means including a lamp receptacle for supporting and providing connection to said incandescent lamp, and switch means having a first primary electrode connected to said input means, a second primary electrode connected to said output means, and a control electrode connected to said. oscillator means, said switching means initiating conduction of said alternating current is of one polarity and said alternating signal exceeds a design level and said switching means ceases conduction when said alternating: current is of a polarity opposite said one polarity, where-- by the power of said alternating current is fluctuated at a rate which varies between 3 and 30 cycles per second.

16. Apparatus according to claim 15 wherein said. oscillator means includes heat sensitive means responsive: to heat generated by said lamp for changing the frequency of oscillation of said alternating signal.

17. Apparatus according to claim 15 wherein said oscillator means comprises a plurality of oscillators, each of said oscillators being connected in parallel to said con verter means and to said switching means, said oscillators providing separate alternating signals each having respective different frequencies and each being different from the frequency of said alternating current or a harmonic thereof.

18. Apparatus according to claim 15 wherein said input attachment means comprises a socket adapted to be assembled to a lamp receptacle of an existing lamp structure, said socket being of the same type as the lamp receptacle supporting said incandescent lamp, and a housing supporting said input and output attachment means and enclosing said converter means, oscillator means, and switching means.

19. Apparatus according to claim 15 further including phase-shift means connected to said control electrode and one of said primary electrodes of said switch means, said phase-shift means being operable to impress a second signal on said alternating signal to determine said design level, said second signal being of the same frequency as said alternating current, said phase-shift means including means for shifting the phase of said second signal relative to said alternating current.

20. Apparatus according to claim 19 wherein said phase-shift means comprises a resistor and a capacitor connected in series between said first and second primary electrodes and said control electrode is connected to the junction of said resistor and capacitor.

References Cited UNITED STATES PATENTS 3,145,323 8/1964 Klotz 315-209 3,397,344 8/1968 Skirpan 3 l5l94 3,435,286 3/1969 Kayatt 31547 3,440,488 4/ 1969 Skirvin 315-209 JOHN W. HUCKERT, Primary Examiner S. BRODER, Assistant Examiner US. Cl. X.R. 

